[PATCH 0/2] Small log simplifications

[PATCH 0/2] Small log simplifications

[Martin von Zweigbergk]

These are just some things I noticed while looking at the revision
walking code. I'm not very familiar with the code at all, so the
patches may very well be completely wrong; view them as newbie
questions in patch-form if you like.


Martin von Zweigbergk (2):
  remove unnecessary parameter from get_patch_ids()
  log: remove redundant check for merge commit

 builtin/log.c | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

-- 
1.7.11.1.104.ge7b44f1

[PATCH 1/2] remove unnecessary parameter from get_patch_ids()

[Martin von Zweigbergk]

get_patch_ids() takes an already initialized rev_info and a
prefix. The prefix is used when initalizing a second rev_info. Since
the initialized rev_info already has a prefix and it seems the prefix
doesn't change, we can used the prefix from the initialized rev_info
to initialize the second rev_info.

Signed-off-by: Martin von Zweigbergk <martin.von.zweigbergk@gmail.com>
---
 builtin/log.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/builtin/log.c b/builtin/log.c
index ecc2793..7a92e3f 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -696,7 +696,7 @@ static int reopen_stdout(struct commit *commit, const char *subject,
 	return 0;
 }
 
-static void get_patch_ids(struct rev_info *rev, struct patch_ids *ids, const char *prefix)
+static void get_patch_ids(struct rev_info *rev, struct patch_ids *ids)
 {
 	struct rev_info check_rev;
 	struct commit *commit;
@@ -717,7 +717,7 @@ static void get_patch_ids(struct rev_info *rev, struct patch_ids *ids, const cha
 	init_patch_ids(ids);
 
 	/* given a range a..b get all patch ids for b..a */
-	init_revisions(&check_rev, prefix);
+	init_revisions(&check_rev, rev->prefix);
 	o1->flags ^= UNINTERESTING;
 	o2->flags ^= UNINTERESTING;
 	add_pending_object(&check_rev, o1, "o1");
@@ -1306,7 +1306,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 			if (hashcmp(o[0].item->sha1, o[1].item->sha1) == 0)
 				return 0;
 		}
-		get_patch_ids(&rev, &ids, prefix);
+		get_patch_ids(&rev, &ids);
 	}
 
 	if (!use_stdout)
@@ -1525,7 +1525,7 @@ int cmd_cherry(int argc, const char **argv, const char *prefix)
 			return 0;
 	}
 
-	get_patch_ids(&revs, &ids, prefix);
+	get_patch_ids(&revs, &ids);
 
 	if (limit && add_pending_commit(limit, &revs, UNINTERESTING))
 		die(_("Unknown commit %s"), limit);
-- 
1.7.11.1.104.ge7b44f1

[PATCH 2/2] log: remove redundant check for merge commit

[Martin von Zweigbergk]

While walking the revision list in get_patch_ids and cmd_cherry, we
ignore merges by checking if there is more than one parent. However,
since the revision walk was initialized with revs.ignore_merges = 1,
this would never happen. Remove the unnecessary checks.

Also re-initializing rev_info fields to the same values already set in
init_revisions().

Signed-off-by: Martin von Zweigbergk <martin.von.zweigbergk@gmail.com>
---
 builtin/log.c | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/builtin/log.c b/builtin/log.c
index 7a92e3f..8182a18 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -726,10 +726,6 @@ static void get_patch_ids(struct rev_info *rev, struct patch_ids *ids)
 		die(_("revision walk setup failed"));
 
 	while ((commit = get_revision(&check_rev)) != NULL) {
-		/* ignore merges */
-		if (commit->parents && commit->parents->next)
-			continue;
-
 		add_commit_patch_id(commit, ids);
 	}
 
@@ -1509,8 +1505,6 @@ int cmd_cherry(int argc, const char **argv, const char *prefix)
 
 	init_revisions(&revs, prefix);
 	revs.diff = 1;
-	revs.combine_merges = 0;
-	revs.ignore_merges = 1;
 	DIFF_OPT_SET(&revs.diffopt, RECURSIVE);
 
 	if (add_pending_commit(head, &revs, 0))
@@ -1534,10 +1528,6 @@ int cmd_cherry(int argc, const char **argv, const char *prefix)
 	if (prepare_revision_walk(&revs))
 		die(_("revision walk setup failed"));
 	while ((commit = get_revision(&revs)) != NULL) {
-		/* ignore merges */
-		if (commit->parents && commit->parents->next)
-			continue;
-
 		commit_list_insert(commit, &list);
 	}
 
-- 
1.7.11.1.104.ge7b44f1

Re: [PATCH 2/2] log: remove redundant check for merge commit

[Junio C Hamano]

Martin von Zweigbergk <martin.von.zweigbergk@gmail.com> writes:

> While walking the revision list in get_patch_ids and cmd_cherry, we
> ignore merges by checking if there is more than one parent. However,
> since the revision walk was initialized with revs.ignore_merges = 1,
> this would never happen. Remove the unnecessary checks.
>
> Also re-initializing rev_info fields to the same values already set in
> init_revisions().
>
> Signed-off-by: Martin von Zweigbergk <martin.von.zweigbergk@gmail.com>

I think the in-loop checks were totally redundant.  I suspect that
explicit initialization to revs.ignore_merges outself can be called
belt-and-braces defensive programming to avoid getting surprised by
future changes to what init_revisions() would do, so I do not have
strong preference either way.

> ---
>  builtin/log.c | 10 ----------
>  1 file changed, 10 deletions(-)
>
> diff --git a/builtin/log.c b/builtin/log.c
> index 7a92e3f..8182a18 100644
> --- a/builtin/log.c
> +++ b/builtin/log.c
> @@ -726,10 +726,6 @@ static void get_patch_ids(struct rev_info *rev, struct patch_ids *ids)
>  		die(_("revision walk setup failed"));
>  
>  	while ((commit = get_revision(&check_rev)) != NULL) {
> -		/* ignore merges */
> -		if (commit->parents && commit->parents->next)
> -			continue;
> -
>  		add_commit_patch_id(commit, ids);
>  	}
>  
> @@ -1509,8 +1505,6 @@ int cmd_cherry(int argc, const char **argv, const char *prefix)
>  
>  	init_revisions(&revs, prefix);
>  	revs.diff = 1;
> -	revs.combine_merges = 0;
> -	revs.ignore_merges = 1;
>  	DIFF_OPT_SET(&revs.diffopt, RECURSIVE);
>  
>  	if (add_pending_commit(head, &revs, 0))
> @@ -1534,10 +1528,6 @@ int cmd_cherry(int argc, const char **argv, const char *prefix)
>  	if (prepare_revision_walk(&revs))
>  		die(_("revision walk setup failed"));
>  	while ((commit = get_revision(&revs)) != NULL) {
> -		/* ignore merges */
> -		if (commit->parents && commit->parents->next)
> -			continue;
> -
>  		commit_list_insert(commit, &list);
>  	}

Re: [PATCH 1/2] remove unnecessary parameter from get_patch_ids()

[Junio C Hamano]

Martin von Zweigbergk <martin.von.zweigbergk@gmail.com> writes:

> get_patch_ids() takes an already initialized rev_info and a
> prefix. The prefix is used when initalizing a second rev_info. Since
> the initialized rev_info already has a prefix and it seems the prefix
> doesn't change, we can used the prefix from the initialized rev_info
> to initialize the second rev_info.

s/it seems the prefix doesn't change/the prefix never changes/;

> Signed-off-by: Martin von Zweigbergk <martin.von.zweigbergk@gmail.com>

I think this change shouldn't change the behaviour and is good.

Just FYI, during the revision traversal, prefix affects two things
in the current code:

 (1) it is used as the basename for prune data that determine which
     parts of the tree structure to pay attention to (e.g. "cd t &&
     git log .").

 (2) it is used as the basename for diff output when revs->diffopt
     is used (e.g. "cd t && git log -p").

And check_rev is used with neither.  It does not want to prune any
part of the tree nor it wants to filter with fancier options like
grep/pickaxe (i.e. it does not use setup_revisions()).

In that sense it probably does not even matter if you did not pass
rev->prefix down to check_rev, and instead gave NULL to it, but that
only holds true in the current codebase, so I think what your patch
does is the right thing to do.

Thanks.

>  builtin/log.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/builtin/log.c b/builtin/log.c
> index ecc2793..7a92e3f 100644
> --- a/builtin/log.c
> +++ b/builtin/log.c
> @@ -696,7 +696,7 @@ static int reopen_stdout(struct commit *commit, const char *subject,
>  	return 0;
>  }
>  
> -static void get_patch_ids(struct rev_info *rev, struct patch_ids *ids, const char *prefix)
> +static void get_patch_ids(struct rev_info *rev, struct patch_ids *ids)
>  {
>  	struct rev_info check_rev;
>  	struct commit *commit;
> @@ -717,7 +717,7 @@ static void get_patch_ids(struct rev_info *rev, struct patch_ids *ids, const cha
>  	init_patch_ids(ids);
>  
>  	/* given a range a..b get all patch ids for b..a */
> -	init_revisions(&check_rev, prefix);
> +	init_revisions(&check_rev, rev->prefix);
>  	o1->flags ^= UNINTERESTING;
>  	o2->flags ^= UNINTERESTING;
>  	add_pending_object(&check_rev, o1, "o1");
> @@ -1306,7 +1306,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>  			if (hashcmp(o[0].item->sha1, o[1].item->sha1) == 0)
>  				return 0;
>  		}
> -		get_patch_ids(&rev, &ids, prefix);
> +		get_patch_ids(&rev, &ids);
>  	}
>  
>  	if (!use_stdout)
> @@ -1525,7 +1525,7 @@ int cmd_cherry(int argc, const char **argv, const char *prefix)
>  			return 0;
>  	}
>  
> -	get_patch_ids(&revs, &ids, prefix);
> +	get_patch_ids(&revs, &ids);
>  
>  	if (limit && add_pending_commit(limit, &revs, UNINTERESTING))
>  		die(_("Unknown commit %s"), limit);

Re: [PATCH 1/2] remove unnecessary parameter from get_patch_ids()

[Martin von Zweigbergk]

On Fri, Jul 27, 2012 at 3:44 PM, Junio C Hamano <gitster@pobox.com> wrote:
> Martin von Zweigbergk <martin.von.zweigbergk@gmail.com> writes:
>
> s/it seems the prefix doesn't change/the prefix never changes/;

:-) Thanks for confirming.

> In that sense it probably does not even matter if you did not pass
> rev->prefix down to check_rev, and instead gave NULL to it, but that
> only holds true in the current codebase, so I think what your patch
> does is the right thing to do.

Makes sense. Thanks for explaining!

Re: [PATCH 2/2] log: remove redundant check for merge commit

[Martin von Zweigbergk]

On Fri, Jul 27, 2012 at 3:30 PM, Junio C Hamano <gitster@pobox.com> wrote:
> Martin von Zweigbergk <martin.von.zweigbergk@gmail.com> writes:
>> Also re-initializing rev_info fields to the same values already set in
>> init_revisions().

Oops, that should have been " _avoid_ re-initializing".

> I suspect that
> explicit initialization to revs.ignore_merges outself can be called
> belt-and-braces defensive programming to avoid getting surprised by
> future changes to what init_revisions() would do, so I do not have
> strong preference either way.

I suspected the same, but OTOH, if it was ever changed, one would have
to go through all call sites anyway. I checked the other calls to
init_revisions (48 of them, I think) and I found only 3 other places
where a field was re-initialized to the same value. In this case it
was done inconsistently even within the file. Seeing init_revisions()
followed by "revs.ignore_merges = 1;" in one place but not the other
can easily lead one to believe that the other place does not ignore
merges.

Do you want a reroll with updated commit messages (the missing "avoid"
above, the dropped "seems like" about the prefix in 1/2)? Since you
don't have a strong preference about the explicit initialization, I
assume I can leave those hunks in. I would clarify my reasoning,
though.

Martin

Re: [PATCH 2/2] log: remove redundant check for merge commit

[Junio C Hamano]

Martin von Zweigbergk <martin.von.zweigbergk@gmail.com> writes:

> Do you want a reroll with updated commit messages (the missing "avoid"
> above, the dropped "seems like" about the prefix in 1/2)?

Nah, I've already queued them with log message tweaks.  Thanks for
asking, though.

Re: [PATCH 2/2] log: remove redundant check for merge commit

[Martin von Zweigbergk]

Sorry, I meant to CC the list. See below.

On Sat, Jul 28, 2012 at 9:56 PM, Martin von Zweigbergk
<martin.von.zweigbergk@gmail.com> wrote:
> On Fri, Jul 27, 2012 at 11:52 PM, Junio C Hamano <gitster@pobox.com> wrote:
>> Junio C Hamano <gitster@pobox.com> writes:
>>
>> It seems to have some interaction with your other topic, though.
>> These two patches alone will pass the existing tests, but merging it
>> with mz/rebase-range breaks t3412.  I didn't look into it, but
>> perhaps this breaks "git cherry" in some way?
>
> Yes, it breaks "git cherry" quite badly, by not ignoring merges at
> all. I incorrectly assumed that ignore_merges was about revision
> traversal, but now I think it's only diff output from 'git log' (and
> possibly others). What I think tricked me was seeing that
> "ignore_merges = 1" closely followed by a comment saying "ignore
> merges". But now I think the explicit code to "ignore merges" is
> necessary (as show by the failing test case), but can be replaced by
> "rev_info.max_parents = 1". Setting "ignore_merges = 1", OTOH, now
> seems doubly redundant: not only does it set the same value as was set
> in init_revisions, but it's also irrelevant. Since cherry doesn't
> generate any diff output, I think ignore_merges is never used.
> Flipping the values of all of "ignore_merges", "combine_merges" and
> "diff" does not have any effect on test cases at least. I hope my
> explanation makes some sense at least...
>
> I'll send a reroll when I get time.

Re: [PATCH 2/2] log: remove redundant check for merge commit

[Junio C Hamano]

Martin von Zweigbergk <martin.von.zweigbergk@gmail.com> writes:

>> I incorrectly assumed that ignore_merges was about revision
>> traversal, but now I think it's only diff output from 'git log' (and
>> possibly others).

Yeah, I realized the same after I wrote the response last night and
went to bed.  I am glad you figured all out yourself.